Rotary wing aircraft, such as helicopters, provide unique environments for the use of ball bearings, particularly in their rotor systems. For example, the bearings in rotor blade mounts must be specially designed to provide reliable ongoing use under the type of load and speed conditions that are unique to helicopters. The use of bearings in other types of machines is nonanalogous to rotary wing aircraft bearings in general and to helicopter bearings in particular. For this reason, bearing designs that are useful in other kinds of machines are not assumed by those of ordinary skill in the art to be suitable for helicopter swashplates, rotor blade mounts, etc.
One example of a conventional rotary wing aircraft bearing is in the tail rotor blade mount of a helicopter such as a Sikorsky CH53A/D helicopter. The blade mount in a Sikorsky CH53A/D helicopter includes a 5-bearing stack of ball bearings. Each bearing in the set is of metric size 70 millimeter (mm)-bore, 110 mm-outer diameter (OD) and 18 mm-width, and has a cross-section of 20 millimeter (mm) [(110-70 mm)/2], which corresponds to a basic 114 ball bearing size that is normally fitted with ½ inch balls. A one-piece, open-ended (one open circular segment) molded nylon cage is used to separate the balls in this bearing. To achieve a minimal cage integrity or strength, to improve cage molding process, and to facilitate cage assembly into bearing, the bearing rings and balls had to be compromised in two respects. First, the bearing ball size of 15/32 inch had to be used instead of balls sized at ½ inch, which would nominally be used in bearings of this size, as noted above. Second, the outer ring face had to be chamfered heavily to accommodate installation of the cage. The chamfer is currently dimensioned as 110° Max by 53° Max, which raises concerns over its adverse effect on the strength of the outer ring, which is under heavy thrust loads in application.
Based on the foregoing, it is the general object of this invention to provide a bearing for a tail rotor assembly that improves upon prior art bearings.